Color photography



INVENTOR.

' ATToRNEYs.

NOV- 14, 1933- o. A. TowNsl-:ND

COLOR PHOTOGRAPHY Filed April 50 .0. 27m/Asme? www Patented Nov. 14,1933 PATENT OFFICE 1,934,779 ooLoR PHo'roGRAPHY Oliver Arnold Townsend,Berhampore, Wellington, New Zealand, assignor to Tru Colour FilmLimited, Wellington, New Zealand Application April 30, 1932, Serial No.608,567, and

in New Zealand June 5, 1931 4 Claims.

This invention relates to photography, and more particularly to theproduction of films for producing natural color pictures.

The object of the invention is to provide an 5 improved process by theuse of which there can be produced colored positive lm wherein colorsare reproduced more naturally and with less exaggeration orartificialness than in positive films produced by known processes, andalso wherein a plurality of colored images can be printed in a singleemulsion common to standard commercial films, so that the colors arenonfugitive or are rendered practically indestructible with ordinaryusage.

The process is simple and can be carried out in any well equipped cineor other photographic laboratory, by means of known apparatus, so as toproduce positive film containing or having incorporated therein anincreased variety of natural color tones, with the images sharply andclearly defined, avoiding fringe or fuzziness, and in the case of a filmused for picture projection, without fiicker and undue loss of light inthe projected picture.

The invention consists, briefly, in producing positive lm by printing apositive image in one side of the emulsion of a single emulsion lm froma negative image formed by a combination of colored light rays;developing said positive image, subjecting the latter to color toningtreatment, followed by controlled fixation treatment; re-converting theuntoned portion of the printed image to a condition in which it willtake further printing; printing through the reverse side of the emulsioninto said reconverted portion of the 'first printed image and unprintedportion of the emulsion, a second positive image from a negative imageformed by a different combination of light rays; developing and fixingsaid second positive 40 image and color toning same so that the twocolored positive images combine to reproduce varying color effects.

The invention further consists in printing the first positive imagelabove referred to, in the outer side of the emulsion, the secondpositive image being printed in the emulsion through the supporttherefor, which order of procedure, together with the color toning ofthe first positive image, and controlled xation of said color 50 toningto provide an unfixed color toned portion, followed by the conversionand utilization of the untoned portion of the rst positive image in theproduction of the second positive image, with development of the latterand said unlixed color. toned portion, and a further colorl toning ofthe aforesaid unxed color toned portion when color toning the secondpositive image, results in there being obtained in the finished positivefilm such an intimate mixture or intermingling of colors, that tones andcolor shades not obtainable with known two color processes, are enabledto be reproduced photographically.

In order that the invention may be better understood, it will now bedescribed in detail, the following being a practical working descriptionof the process.

The one figure of the attached drawing diagrammatically illustrates myinvention more elaborately described in the following description:

Standard single emulsion film is used in the formation of the positive,the latter being printed from a negative film or films the images onwhich have been obtained with or without the aid of separate, orcombined red and yellow or orange, and blue or blue green lters,screens, or color selectors, in any known manner, by the use of anysuitable cameras.

In order to produce the positive film, a positive image of suitableweight is printed in the outer side of the emulsion of the film from anegative image formed by red orange yellow green light rays, to producean image representing the blue green portion and developed by means of asuitable developer, a developer consisting of sodium 85 sulphite,potassium metabisulphite, diamidopheno1 hydrochloride and water, beingfound to give good results in this connection.

Following the development of the positive image just printed, the filmis Washed for approximately five minutes, and toned blue in a bathconsisting of ferrie chloride, oxalic acid, nitric acid, potassiumferricyanide, and water, said ingredients being lused in the followingproportionsz-ferric chloride 36 grains to 72 grains, but preferably 48grains; oxalic acid 6 grains to 20 grains, but preferably 121/2 grains;nitric acid approximately 180 minims; potassium ferricyanide 48 grainsto 96 grains, but preferably 60 grains, and water approximately 240 uidounces.

The treatment of the lm in this last mentioned toning bath, results inthe blue tone being absorbed or deposited only in that portion of thepositive image in the outer layer o1: portion of the emulsion, so thatwhen the depth of the image varies or is irregular, shallow portions orthe half tones of said image, are fully toned or colored, while portionsof the image of greater depth than said shallow portions or half tones,are not toned lo or colored for their full depth, the remaining'orunblued reduced silver of said deeper portions or shadows beingconverted to silver 'ferrocyanide The film is then rinsed, andafterrinsing is treated in a bath consisting of sodium thiosul phate 1%ounces to 8 ounces, but preferably-2 ounces 34 grains; potassiummetabisulphite 1/2 ounce to 2 ounces, but preferably 3A ounce 34 grains;and w ter approximately 240 fluid ounces, which dissolv s out the silverferrocyanide from the blue toned portion of the image and securesfixation thereof, the fixation being controlled by time and temperatureso as to leave an unfixed bluetoned portion below the fixed blueportion, while the silver, ferrocyanide in the deeper portions of theimage is not toned blue, together with more or less, or some of theremaining silver bromide, is converted to insoluble silverthiosulphate.- The fixation of the upper or outer layer of the bluedportion of the image by the last described treatment preventsanyre-development of said 1 layer during further treatment of the lm,and so gives where there is no underlay of red or yellow, the necessaryblue where required fihn is now rinsed in water. e

To print on the other side ofthe film and in orderto enable the positivefilm therein to satisfactorily-receive a print from the negative imageformed by the violet blue green yellow light rays, that part of theemulsion not now consisting of silver bromide, excepting the fixed bluedportion of the image, yis converted to silver bromide, this beingeffected by immersion of the latter in a bath of ammonium carbonate 1A;ounce to 2' ounces, but preferably 3A ounce; ammonium bromide 1/53 ounceto 1/2 ounce, but preferably M; ounce, or the equivalent amount ofbromine as a salt of this halogen; and water approximately 240 uidounces, which bath also has the eect of clearing out any blue stainremaining in the.

emulsion. That part or parts of the emulsion which does consist ofsilver bromide at the time of the reconversion operation isor are moreor less re-sensitized during the latter, such refsensitizingfacilitating the obtaining of a ne grained second positive image, in thereverse side of the emulsion.

In preparing the bath last referred to it is advisable to first dissolvethe ammonium carbonate in the water which has been boiled for thepurpose, and allow the solution to cool before adding the ammoniumbromide.

The film is then rinsed and dried in a suitable light, and the secondpositive image obtained by printing from the negative image formed bythe violet blue green yellow light rays, into the converted silverbromide portion of the rst positive image and the remaining silverbromide of the emulsion, the printing being done through the emulsionsupport. The last mentioned or second positive image is then developedby means of a suitable developer, fixed in a hypo bath, washed, andtoned in a yellow red bath of uranium nitrate 1/4 ounce to 1/2 ounce,but preferably. 1,41 ounce 50 grains; oxalic acid 60 grains to 100grains, but preferably grains; nitric acid approximately 11/2 ounces;potassium ferricyanide 5g grains to grains, but preferably '75 grains;and water approximately 160 fluid ounces.

Unless otherwise specied, proportions of ingredients are by avoirdupoissystem of weights.

The positive film is then xed in a hypo bath, to reduce graininess andbrighten the whole picture, and can be`given such treatment in anappropriate bath or baths as maybe desirable for support.

the purpose of intensifying any particular color or colors. f n

What I do claim and desire to obtain by Letters Patent of the UnitedStates of America isz- 1. A process for use in the production ofphotographic with registering differently colored positive imagesthereon, consisting in printing an image in the outer side oi. theemulsion of a single emulsion film from a negative image formed by red,orange, yellow, green light rays; developing said image; subjecting the4latter to treatment in a blue bath, whereby part of the image is bluetoned, subjecting the partly blue toned image to controlled fixation toprovide a fixed and an unfixed blue toned portions; reconverting theuntoned portion of the image to silver bromide; printing a secondpositive image through the emulsion support into the reconverted portionof the first printed positive image and the unprinted silver bromide ofthe film, from a negative image formed by violet, blue, green, yellowlight rays, developing and fixing said second positive image and colortoning Asame and the unfixed color toned portion of the first image, ina yellow red bath.

2. The processl of producing a photographic film having differentlycolored outer and inner superposed images therein which consists inprinting and developing said images, but before fixing the film toningthe outer image blue in a blue bath constituted to tone the outer imagewithout' af- 105 fecting the inner image to the extent that the shallowor top portions of said outer image are completely toned Whilst deeperportions of said outer image are not toned completely, converting thenon-completely toned portions of the outer 1 19 image into silverferrocyanide, rinsing` and xing the entire film, toning the second imagein a penetrating red yellow bath, rinsing the film and fixing the redyellow toned image.

3. The process of producing photographic lm having differently coloredpositive images in opposite surfaces of ra single emulsion whichconsists in printing an image from a negative formed by red orangeyellow green light rays on the outer side of an emulsion, thendeveloping said image, washing the film and toning the image blue o theextent that the shallowportions of said o ter image are fully tonedwhile portions of the image of greater depth are not completely toned,the remaining or deepest portions being converted to silverferrocyanide, rinsing the film and treating the same in a bathcontaining sodium thiosulphate to dissolve outA the iron silverferrocyanide from the fully blue toned portion of y in a bath containingammonium bromide and ammonium carbonate to convert all the insolublesilver thiosulphate in the emulsion to light sensitive silver bromide,and printing on the opposite side of the emulsion an image from a;negative formed by violet blue green yellow light rays.

4. Aprocess as claimed in claim -2 in which the differently coloredouter and inner superposed images are ma'de on the same side of a commonOLIVER ARNOLD TOWNSEND.

